Decoding apparatus for use in matrix four channel systems of a plurality of types

Claim 1

A decoding apparatus for use in matrix four channel systems of different types comprising: first and second input terminals adapted to receive first and second composite signals to be decoded respectively; first to fourth output terminals from which first to fourth output signals are derived out; first phase shifter circuit means coupled to said first input terminal for producing a third composite signal; second phase shifter circuit means coupled to said second input terminal and having substantially the same phase shifting characteristic as said first phase shifter circuit means; matrix circuit means having first and second inputs, the second input of said matrix circuit means being coupled to said second input terminal of said decoding apparatus, said matrix circuit means being operative to produce a sum of input signals when they are applied to said first and second inputs of said matrix circuit means; first switch means coupled between said first input of said matrix circuit means and said first input terminal of said decoding apparatus for selectively coupling said first input terminal of said decoding apparatus to said first input of said matrix circuit means in accordance with the type of the first and second composite signals to be decoded; third phase shifter circuit means coupled to the output of said matrix circuit means and having a different phase shifting characteristic from said first and second phase shifter circuit means; second switch means for selectively deriving out an output signal from said second phase shifter circuit means and an output signal from said third phase shifter circuit means in accordance with the type of said first and second composite signals to be decoded to provide a fourth composite signal, said second switch means being adapted to selectively derive out the output signal from said second phase shifter circuit means as said fourth composite signal when said first switch means couples said first input terminal of said decoding apparatus to said first input of said matrix circuit means; and signal combining means adapted to generate first to fourth output signals on said first to fourth output terminals respectively by combining said third and fourth composite signals, when said first input terminal of said decoding apparatus is not coupled with said first input of said matrix circuit means and generate the first and second output signals on said first and second output terminals respectively by combining said third and fourth composite signals, and the third and fourth output signals on said third and fourth output terminals respectively by combining said third and fourth composite signals and a fifth composite signal which is produced by said third phase shifter circuit means when said first input terminal of said decoding apparatus is coupled to said first input of said matrix circuit means.